I'm a bit outdated on the matter, but IIRC they supported 3 loading methods: non-homebrewed through smash stack, homebrewed through riivolution, and homebrewed through ocarina codes.The disc is required to run through smash stack and riivolution, but running through ocarina (the file replacement code in the .gct to be exact), you can use several apps, namely gecko os (also requires a disc) and most, if not all, usb loaders to run project M. Just place the files in your sd card as instructed, enable ocarina codes in your usb loader of choice, and you should be good to go.Hope this helps ps: sorry for any spelling/grammar mistakes, and for the lack of paragraphs, i'm having trouble formatting my post